Conventional building industry practice uses prefabricated door frame assemblies which are manufactured at a manufacturing facility and then transported to a remote location for installation. This door frame includes a header assembly for the top of the doorway opening and latch and hinge jamb assemblies for the sides of the doorway opening in the wall.
The thickness of the wall in which the door is to be located often varies. These variations result from variations in the standard materials used as well as in the assembly of those materials in forming the walls. To accommodate these thickness variations in the wall, the frame must be adjustable.
Additionally, the frame should be adaptable to a wide variety of uses, including the addition of a screen or storm door and the addition or omission of exterior trim.
To minimize expenditures in manufacturing, the latch and hinge jamb assemblies and the header assembly should be of generally the same construction.
With the increasing cost of wood, metal frames, particularly those of steel, have become viable for residential use, as well as for commercial use. Thus, the use of metal door frames is expanding.